Elastic fluid turbine arrangement



2 1941. A. H. BUEHMAN 2,252,456

ELASTIC FLUID TURBINE ARRANGEMENT Filed April 30, .1940

Fig.1. 2

' .aws\\\\ I 2 9 Inventor":

Albert H. Buehvhan,

His Attorney.

Patented Aug. 12, 1941 UNITED STATES PATENT OFFICE ELASTIC mm TURBINE ARRANGEMENT Albert H. Buehman, Swampscott, Mass, assignor to General Electric Company, a-corporation of New York Application April 30, 1940, Serial No. 332,492

4 Claims.

The present invention relates to elastic fluid turbine arrangements, more vspecifically to arrangements for turning the rotor of an elastic fluid turbine after the turbine has been shut down in order to assure. uniform cooling of the k ing drawing.

In the drawing, Fig. 1 is a diagrammatic view of an elastic fluid turbine-arrangement embodying my invention, and Fig. 2 is an en1arged,detail view of a part of Fig, 1.

The arrangement comprises an elastic fluid turbine ID with an inlet conduit H including a stop or emergency valve 12 and a throttle valve 2 l3. The throttle valve 13 is controlled by a speed governing mechanism in response to speed changes of the turbine. This speed governing mechanism comprises a speed governor I4 driven by a beveled gearing l from a shaft; secured to or forming part of the turbine rotor and supported by means including a-turbine bearin Ilia. Movement of the speed governor upon speed changes of the turbine rotor is transmitted tov the throttle valve I3 by means including a;..

ydraulic motor l1 and a pilot valve [8. The motor I! has a piston IS with a stem connected to the left-hand end of a lever2lwhich has an intermediate point held on a fulcrum 22 and a right-hand end pivotally connected to the f throttle valve 13. The pilot valve l8 whichl-ike the motor I! is of well known construction has valve heads secured to a stem 23 which is'pivotally connected to an intermediate point of a floating and follow-up lever 24. The right-hand 1 end of the lever 24 ispivotally connected to the piston stem 2'0 and the left-hand end of the lever 24 is pivotally connected to the speed governor Id. The pilot valve I8 is connected to the motor I! by means including ports 25 and 255 normally covered by the pilot valve heads: Operating ,fluid under pressure such as oil is conducted to to the pilot valve by a pipe 21 from a main source of supply.

During normal operation,

with the stop valve I2, in open position, an increase in speed causes downward movement of the pilot valve heads whereby fluid under pressure is conducted to the lower side of the piston I9 and discharged from the upper side thereof, thereby. causing upward movement of the piston l9. This. efiects closing movement of the throttle valve l3 and also upward movement of the l pilot valve heads whereby the latter are restored to. their normal position in which they cover the ports 25 and 26. During decrease in .speed the operation of the speed-governing mechanism is similar except that thevariouselements movein opposite directionto effect open ng movement of the valve During shut-down, for instance, withv the stop Valve 12 in closed position, the turbine rotor may be turned mechanically. The power agency .for mechanically turning or'rotating the turbine rotor in the present instance is in the form of an electric motor 28 connected by an electric circuit 29 to a source of electricenergy 30. The circuit 2.9v includes contacts 3| bridged by a contactaking member 32 which is biased towards the contacts by a compression spring 33. Openin of the valve 12 effects movement of the contactmaking, member 32 away from the contacts 31 .and.1ikewise., closingof the valve 12 automatically causes closing of 'theecontacts 31 by the action of the compression spring 33. Thus, opening and closing of the stop valve 12 automatically causes opening and closing respectively of the circuit 29 for the motor 28. The motor 28 which serves for rotating the turbine rotor, as will be more fully described hereinafter, also serves for driving an auxiliary pump 34. for supplying oil to the turbine bearing Ilia and to the hydraulic. motor during shut-down period and also upon failureof. the main oil supply. The pump 34 ,which is driven from the shaft of the motor 28 has an inlet 35 forreceiving oil and a discharge 36 connected by a pipe 31 to two pipes 38 and 39. The pipe, 38 is connected with the turbine bearing and the pipe 3.9 is connected to the aforementionedconduit 21. The pipe .31 includes a check valve and the pipe 21 includes another check valve 4! arranged ahead of the connection ofth-e pipe 21 with the pipe 39 as regards the direction'of flow of fluid from the main source of supply through the pipe 21. During normal operation of the turbine, oil is supplied from the main source through the pipe 21 to the pilot 'valve and the hydraulic motor and from the pipe 21 through the pipes 39, 38 to the turbine bearing 16a. During this condition the check valve 43 prevents flow of oil from the pipe 39 into the pipe 31,

During operation of the turning motor 28 and the auxiliary oil pump 35, oil is supplied through the conduit 31 and the conduit 38 to the turbine bearing and from the conduit 31 through the conduit 39 to the hydraulic motor. During this condition, in which the turbine rotates at a low speed of the order of a few revolutions per minute, the piston IQ of the hydraulic motor is held in its lowermost position, thereby keeping the throttle valve 13 fully open and permitting quick starting of the turbine by opening of the stop valve l2.

Upon failure of the main source of oil supply, the motor 28 may be automatically started to maintain the oil supply to the bearing and the hydraulic motor by action of the auxiliary pump 34. The automatic starting of the motor 28 in response to failure of the main oil supply is accomplished by means including a pressure-responsive device in the form of a bellows 42 having an upper end connected by a pipe 43 to the pipe 21 ahead of the check valve 4| as regards the direction of flow of fluid from the main source of oil supply. The lower end of the bellows 42 carries a contact-making member 44 which, in the position shown, bridges two contacts 45 connected by wires 46 in parallel to the aforementioned contacts 3|. As the oil pressure in the pipe 21 drops to a certain low value, the contacts 45 are closed, thereby bridging the contacts 3| and closing the circuit 29 of the motor other elements requiring fluid under pressure during operation. Thus, operation of the auxiliary oil supply pump may be automatically effected upon failure of the main oil supply by closing of the contacts 45, and also upon shutting down of the turbine. by closing the stop valve l2.

During shut-down. of the turbine, the turning motor 28 is automatically, mechanically coupled to the turbine shaft l6 as thespeed of the turbine shaft drops to a predetermined low value. The arrangement for connecting and disconnecting the shaft of the motor 28 to the turbine shaft l includes a worm 41 driven from the turning motor 28 and engagin a gear .48 which is rotatably supported on a fixed shaft 49, Fig. 2. The shaft 49 is securedto a stationary support 5|] by a pin 5|. Axial movement of the gear 48 on the shaft 49 is limited by. a washer 52 and a nut 53 secured to the shaft 49. A coupling or clutch half 54 of a tooth coupling is centrally arranged with and in the present instance integrally formed with the gear 48. Another half 55 of this coupling is supported on a .splined shaft 55, aligned with and securely fastened to the shaft l6 by a connecting and supporting member 51. A compression spring58 surrounding the splined shaft 56 and arranged between adjacent surfaces of the coupling half 55 and the connectingmember 51 biases the coupling half 55 towards the left, that is, into engagement withthe other coupling half 55. During normal. turbine ope-ration, that is, at high turbine speed, engagement of the coupling half is prevented by the action of two fiyweights 59, 60 which are pivotally supported on the connecting and supporting member 5'l'and have arms or fingers 6| engaging the coupling half 55 to bias the latter towards the right, that is, away from the other couplin half 54, against the spring 58 with a force which increases as the speed increases until the flyweights 59 and 60 rest against stops 62, thereby holding the coupling half 55 completely disengaged from the coupling half 54.

In the position shown in the drawing, the valve I2 is closed and the coupling or clutch 54, 55 is engaged, whereby the turning motor 28 rotates the turbine rotor at a low speed of the order of a few R. P. M. and also operates the pump 34 to supply oil to the bearing and the hydraulic motor as described above. If, now, the valve I2 is opened and elastic fluid is supplied to the turbine, the turbine rotor at first is driven by both the action of the elastic fluid and the motor 28. Due to the action of the elastic fluid supplied to the turbine, the rotor will begin to speed faster than the turning gear, and the teeth of the coupling half 55 will successively override the opposite teeth of the coupling half 54, alternately compressing the spring 58. This action takes place faster and faster as the turbine speed increases until, at the desired speed for which designed, the flyweights 59, 60 are forced out by the action of centrifugal force sufficiently to withdraw the coupling half 55 completely from the half 54. Thereupon, the turbine continues to operate entirely independently of the turning motor 28. If the stop valve I2 is sufficiently opened to effect opening of the contacts 3|, the motor 28 is disconnected, provided that oil is supplied from the main source and the contact-making member 44 is held in opening position by the pressure-responsive device 42.

If the turbine is shut down, for instance by closing of the stop valve l2, the circuit of the motor 28 is closed. As the turbine speed drops to a value at which the fiyweights will release the coupling half 55, allowing it to slide towards the coupling half 54 by action of the spring 58, the coupling will engage, though at first the coupling half 55 will override on the teeth of the coupling half 54. As the turbine speed has dropped to a speed equal to or slightly below the speed of the coupling half 54, the turbine rotor will be positively driven by the turning motor 23.

Though in general not desirable, the turbine may be operated, that is, started and stopped without the turning motor. The circuit of the latter may be disconnected from the line 30 by a switch 63.

The spring 58 is comparatively light, that is, only of a strength suflicient to overcome the sliding friction of the coupling half 55 on the splined shaft 55. With a light spring, the flyweights upon acceleration of the turbine rotor may throw out, that is, effect disengagement of the coupling at low speed. Also, each time the teeth of the coupling override as the turbine shaft overspeeds the turning gear, the coupling half 55 is forced against the spring 58, thereby assisting thefflgweights 59, 6B in withdrawing the coupling ha 5.

Thus, with my invention I have accomplished an improved construction and arrangement of turbine turning gear mechanisms which include a turning motor connected to the turbine shaft by means including a coupling or clutch having halves mechanically connected to the turning motor and the turbine shaft respectively, and mechanical means for effecting engagement and disengagement of the coupling in response to certain speed changes of the turbine. The turning motor of my invention may also drive an auxiliary oil pump for forcing oil to bearings and to a hydraulic motor during operation of the turbine turning mechanism and also upon failure of the main oil supply. During turning operation the auxiliary oil pump supplying oil to thehydraulic motor holds such motor in a position in which the turbine throttle valve is held fully open, thereby permitting quick starting of the turbine by opening of a stop valve.

Having described the method of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Elastic fluid turbine arrangement comprising a turbine having an inlet conduit with a stop valve and a throttle valve, a rotor with a shaft and a bearing for the shaft, a speed governing mechanism including a speed governor driven from the shaft and hydraulic means for moving the throttle valve in response to speed changes of the turbine, means normally supplying oil under pressure to the hydraulic mechanism, means including a turning motor for slowly rotating the turbine rotor upon shut-down, and means including a pump driven by the turning motor for supplying oil under pressure to the hydraulic mechanism and to the bearings upon shutdown of the turbine and upon failure of the main oil supply and a device responsive to oil pressure from the main oil supply automatically to effect starting of the turning motor as the pressure of the main oil supply drops to a predetermined low value.

2. Elastic fluid turbine arrangement comprising a turbine having a rotor and an inlet conduit with a stop valve, and means for rotating the turbine rotor upon shut-down of the turbine, said means including a turning motor, an electric circuit for the motor including a contact-making device in cooperative relation with the stop valve automatically to close the circuit upon closing of the stop valve.

3. Elastic fluid turbine arrangement comprising a turbine having a rotor with a shaft, a bearing supporting the shaft and an inlet conduit with a stop valve and a throttle valve, means normally supplying oil under pressure to the bearing, means for rotating the turbine rotor upon shut-down, said means including a turning motor, an electric circuit for the motor including a contact-makingdevice in cooperative relation with a stop valve automatically to close the circuit upon closing of the stop valve,

means including an auxiliary oil pump driven by the turning motor to supply oil to the bearing during shut-down of the turbine and at the same time to maintain the throttle valve in open position to permit quick starting of the turbine.

4. Elastic fluid turbine arrangement comprising a turbine having a rotor and an inlet conduit with a valve, a motor for turning the rotor, and means including a device cooperatively associated with the valve for automatically starting the motor as the valve is moved into closing position.

ALBERT H. BUEHMAN. 

